refactor(delib-1c/1d/1e/1f): un-link-libc — full migration

build.zig

@@ -28,16 +28,18 @@ pub fn build(b: *std.Build) void {
     options.addOption([]const u8, "version", build_zon.version);
 
     // Library module (for use as dependency and test root).
-    // link_libc is required because wasi.zig / cache.zig / platform.zig use
-    // `std.c.*` for POSIX operations that std.posix lost in Zig 0.16
-    // (fsync, mkdirat, unlinkat, renameat, dup, pread/pwrite, futimens, …).
-    // On Linux the build is strict about this; macOS happens to auto-link
-    // libc for `extern "c"` decls but both platforms need it.
+    // link_libc = false post-W46 migration. WASI fd I/O and path-based ops
+    // now go through `platform.pfd*` helpers (Linux syscalls / Mac libSystem
+    // auto-link / Win32 kernel32). Env vars come from `std.process.Environ.Map`
+    // captured in `cli.main` (W46 Phase 1e). The `std.c.*` references that
+    // survive are all inside `else` branches of `switch (comptime builtin.os.tag)`
+    // blocks, so they are comptime-pruned on Linux/Windows and still resolve
+    // to libSystem on Mac.
     const mod = b.addModule("zwasm", .{
         .root_source_file = b.path("src/types.zig"),
         .target = target,
         .optimize = optimize,
-        .link_libc = true,
+        .link_libc = false,
     });
     mod.addOptions("build_options", options);
 
@@ -55,7 +57,7 @@ pub fn build(b: *std.Build) void {
         .root_source_file = b.path("src/cli.zig"),
         .target = target,
         .optimize = optimize,
-        .link_libc = true,
+        .link_libc = false,
     });
     cli_mod.addOptions("build_options", options);
     const cli = b.addExecutable(.{
@@ -82,7 +84,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path(ex.src),
             .target = target,
             .optimize = optimize,
-            .link_libc = true,
+            .link_libc = false,
         });
         ex_mod.addImport("zwasm", mod);
         const ex_exe = b.addExecutable(.{
@@ -99,7 +101,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("test/e2e/e2e_runner.zig"),
             .target = target,
             .optimize = optimize,
-            .link_libc = true,
+            .link_libc = false,
         });
         e2e_mod.addImport("zwasm", mod);
         const e2e = b.addExecutable(.{
@@ -116,7 +118,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("bench/fib_bench.zig"),
             .target = target,
             .optimize = optimize,
-            .link_libc = true,
+            .link_libc = false,
         });
         bench_mod.addImport("zwasm", mod);
         const bench = b.addExecutable(.{
@@ -135,7 +137,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("src/fuzz_loader.zig"),
             .target = target,
             .optimize = optimize,
-            .link_libc = true,
+            .link_libc = false,
         });
         fuzz_mod.addImport("zwasm", mod);
         const fuzz = b.addExecutable(.{
@@ -148,7 +150,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("src/fuzz_wat_loader.zig"),
             .target = target,
             .optimize = optimize,
-            .link_libc = true,
+            .link_libc = false,
         });
         fuzz_wat_mod.addImport("zwasm", mod);
         const fuzz_wat = b.addExecutable(.{
@@ -162,6 +164,12 @@ pub fn build(b: *std.Build) void {
     // Default to ReleaseSafe: Zig 0.15's Debug-mode shared libraries
     // crash on Linux x86_64 due to GPA/PIC codegen issues (see #11).
     // Users embedding zwasm want optimized code anyway.
+    //
+    // C API targets keep link_libc = true: `src/c_api.zig` uses
+    // `std.heap.c_allocator` as the default backing allocator, which
+    // requires libc on every platform (Mac libSystem auto-linked, Linux
+    // glibc/musl, Windows msvcrt). Consumers of libzwasm are C programs
+    // that always link libc anyway, so this costs them nothing.
     const lib_optimize = b.option(bool, "lib-debug", "Build libraries in Debug mode (default: false)") orelse false;
     const lib_shared_mod = b.createModule(.{
         .root_source_file = b.path("src/c_api.zig"),

src/cli.zig

@@ -23,6 +23,7 @@ const component_mod = @import("component.zig");
 const guard_mod = @import("guard.zig");
 const jit_mod = vm_mod.jit_mod;
 const cache_mod = @import("cache.zig");
+const platform = @import("platform.zig");
 
 /// Process-wide Io handle. Populated once at the top of `main` from the
 /// `std.process.Init` the compiler-generated entrypoint hands us, and read
@@ -40,6 +41,12 @@ pub fn main(init: std.process.Init) !void {
 
     cli_io = init.io;
 
+    // Expose the process environment to `platform` so subsequent callers
+    // (`appCacheDir`, `tempDirPath`) can look up HOME / TMPDIR / … without
+    // going through `std.c.getenv` — a prerequisite for dropping
+    // `link_libc = true` on Linux (W46 Phase 1e).
+    platform.setEnvironMap(init.environ_map);
+
     // `init.gpa` is a DebugAllocator-backed allocator in Debug builds
     // (leak-checked by start.zig) and the appropriate production allocator
     // otherwise. `init.arena` is the process arena — args/environ live there.